handling missing data

[BubikolRamios]

suppose I have simple x/y chart, drawing lines on it
x axis having months, y having prices

Two items, prices:

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month                  1     2      3      4   5 
item1/price            3     4                 4 
item2/price            4     4      5

so I suppose there should be:
1. breaked lines on graph(to be clear, I don't want points for item 1 between 2 and 5 months to be connected)
2. added missing months (there should month 4 on x axis but nothing on plot for it)

Need general guidance about this, new to freeChart, and simple things that I have now puts out x axis without 4. month, obviously ....
is there a simple sollution like sending in null (or something) instead of missing price ?
EDIT: tested last sentence, null=0, which then plots wrong chart.

[skunk]

Try using Double.NaN for missing data

[BubikolRamios]

Thanks for replay.

Ok just figured it out, if I send 'real' null, then it works. Does not draw anything where null is.

if I have data like this , by month: 1 null 3 null 5 6
then there is is just line between 5 and 6, I would expect dot at 1 and 3 (nothing currently), but I guess , for that I have to add dots on all points, or not ?

[BubikolRamios]

yes.

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renderer.setSeriesShapesVisible(0, true);

does the trick, but looks ugly, I gues making custom shape will be the quickes way to solve that.